3 Answers
3

The options in the resulting figure are inherited from the first term, namely Graphics[simplePrimitives]. This does not include the "TransparentPolygonMesh" -> True generated by RegionPlot. You see the mesh as a result. If you combine things as follows:

Show[complicatedRegionPlot, Graphics[simplePrimitives]]

Then the resulting image will have the standard RegionPlot options and you'll no longer see the mesh.

I think the preferred way to do this, however, is to use Epilog, as in J.M.'s response.

+1 for explaining why the mesh shows up in addition to fixing the problem
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Thies HeideckeFeb 6 '12 at 13:44

What OS are you using? I see no mesh at all. I wonder if the mesh is a Mac-only thing.
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SzabolcsFeb 6 '12 at 14:04

The simplest solution in some sense although the others work as well.
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DrorFeb 6 '12 at 14:49

@Szabolcs I used V8.0.4 on Mac OS X. I can confirm that V8.0.0 on Windows running in Virtual Machine displays no Mesh. That's odd. The inconsistency seems to be a bug to me.
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Mark McClureFeb 6 '12 at 15:21

Just a guess: Maybe graphics rendering is done differently on different platforms (or different modes are enabled by default), and some idiosyncrasy of the Mac rendering forced the developers to use this workaround. I noticed that @Heike's screenshot is not antialiased. Antialiasing is missing on Windows only when hardware accelerated rendering is used (this mode is automatically turned on e.g. if a Polygon with different VertexColors is included, but it's usually off)
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SzabolcsFeb 6 '12 at 15:42

On that note: if you just want to tack on simple graphics primitives (e.g. Point[], Line[]) to your plots, the use of either the Prolog or Epilog options looks slightly neater than using Show[].
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Guess who it is.♦Feb 6 '12 at 13:58

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